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Re: Manufacture new Bygraves?
From: Thomas Kleemann
Date: 2009 Jul 10, 01:23 +0200

my text woven in below... glapook@pacbell.net schrieb: > You're close to the original Bygave which has a cotan scale 8.8 meters > long. But you would have to adjust your spacing slightly because there > can only be 44 turns between 20' and 89�40' since each turn must equal > a change in log cotan of .1. The log cotan of 89� 40' is about -2.2 > and the log cotan of 20' is about 2.2, a range of 4.4 making 44 > changes of .1 which is the reason for the 44 turns on the original > Bygrave. I did't get that. Do you mean, there is some restrictin in the spacing - that one turn on the scale has to have a certain interval (0.1) covered? I thought I'm free to choose whatever diameter I like and that the scales length divided by the circumference gives the approximate number of turns. Why 44, then? Or do you just talk about the original dimensions? > Its tube is 2.5 inches in diameter Well, 2 inches was just an example... I took it, because anything between 40 and 50mm diameter handles well, haptically. > times Pi makes the > circumfance of 7.85 inches times 44 turns equals 345.58 inches or 8.77 > meters. If you adjust the spacing but keep the pitch unchanged and > make 56 turns it would cover a range of 1'30 to 89� 40' and so > eliminate the problem of sun sights near the equinoxes. > How so? By prolonging the scale down to values below the original 0� 20'? Twelve turns for 19 minutes of arc? Regards, Thomas. --~--~---------~--~----~------------~-------~--~----~ NavList message boards: www.navlist.net Or post by email to: NavList@navlist.net To , email NavList-@navlist.net -~----------~----~----~----~------~----~------~--~---

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